Process for the manufacture of esters



J. A. STEFFENS." PROCESS FOR THE MANUFACTURE OF ESTEBS. APPLICATION FILED APR. 5I 1921.

PatentedJuly 4, 1922..

JOHN A. STEFIEENS, OF BALTIMORE, MARYLAND, ASSIGNOR TO U. S. INDUSTRIAL i ALCOHOL 00., A CORPORATION OF VIRGINIA.

' Application filed April 5,

T 0 all tohom may concern: i V i Be it known that I, ;.J OHN A. STEFFENS, a

citizen of the United States, residing at Baltimore and State of Maryland, have mvented certain new and useful Improvements is added to the alcohol and acid to be esterified athird liquid that is miscible with the alcohol but substantially immiscible with water and which will enable vapors 'to be obtained containing a considerable percenta e of watenin addition to the alcohol and t e third liquid. The vapors are evolved in the form of a ternary mixture of the three constituents. This third liquid may be any one of a number of different compounds such, for example, as benzol, toluol, carbontetrachloride or hexane, but I prefer to use benzol. One of the objects of my invention is to avoid the necessity of using a large amount of benzol in carrylng out the process.

Again, another object is to obtain a con densate rich in water while placing only a small load upon the auxiliary apparatus.

Still another object is to conduct the process of esterification without the aid of a catalyst. r

' A further object is to obtain a drier benzol owing to the separation of the condensate before introducing water into the' same.

Further objects of my'invention will appear from the detailed description thereof hereinafter.

hile my invention is capable of being embodied in many different forms, for the purpose of illustration, I shall describe only certain ways of carrying out my lnvention, and while the same is capable of use with Specification of Letters Patent.

PROCESS FOR THE MANUFACTURE OF ESTERS.

Patented July 4, 1922. 1921; Serial No. 458,837. I

many different types of apparatus I have shown only one type of apparatus'for use therewith'ln the accompanying drawings, in which- The figure is a diagrammatic representatron of an apparatus which may be used in connection with my invention. In the drawings, I have shown a still heated by a steam coil 2 and provided;.with a valved draw-01f. pipe 3. The materials for the. reaction are introduced through a valved pipe 4 whlch in case ethyl lactate is to beformed are comprised of one chemical equivalent of lactic acid having a strength of 80%, the remainder being water, and two to three chemical equivalents of ethyl alcohol having a strength of 95%, or if desired, absolute alcohol, together with an amount of benzol equal in volume to one-half the volume of the alcohol. in the still 1- at a temperature of approximately 80 C. The lactic acid and alcohol react to form ethyl lactate with the liberation of water, and a mixture of water, benzol and alcohol vapors passes out of the still .1 by a pipe 5 to a column rectifier 6 from the lower end of which alcohol and benzol are returned by a liquid sealed pipe 7 to the still 1. From the top of the column 6 vapors containing 7% by weight of water, 74% by weight of benzol and 19% v by weight of alcohol pass off by a pipe 8 to a dephlegmator 9,- cooled with a water current passing through inlet and outlet pipes 10 and 11, and from which some of the condensate passes back by a liquid sealed pipe 12to the top of the column 6. Vapors from the de-' Y phlegmator 9 are conveyed by. the pipe 12 to a condenser 13 cooled with a Water current supplied through inlet and outlet pipes 14 and 15, and from which the condensate passes by a pipe 16 to a vented sight glass 17 arranged to convey part of the condensate by a pipe 18 back to the pipe 12 and thence to the column 6 where the remainder of the condensate is conducted by a pipe 19 to a tail-box 20. The condensate is now carried by a pipe 21 to a separating chamber 22 where it separates into two liquids, the upper layer of which contains 81% by weight of benzol, 15% by weight of alcohol and 4% by weight of water, the lower layer contain- These are distilled 5 ing 35% by weight of Water, 55% by weight of alcohol and 10% by weight otbenzol. The upper layer comprised principally of benzol is conveyed away by a vented liquid sealed overflow pipe 23 to the column 6 while the lower layer is conducted by a liquid sealed pipe 24 to the lower portion of a scrubber In the scrubber water is added through a valved inlet pipe 26 to remove the remainder of the-benzol which is conveyed back by a vented inlet pipe 2Z totlie pipe 23. The water layer 'm t e scrubber then passes out by e same by a vented liquid sealed pipe 28 to a dilute alcohol column 29 provided with an inlet for steam 30 and an outlet for water 31 at the bottom of the column. The column 29 rectifies the alcohol received therein, the alcohol vapors passing up from the same by means of a pipe 32 to a dephlegmator 33, -which has. the 'usual water cooling system, and a liquid sealed return pipe 34 to the top of the column 29.,

The vapors from the dephlegmator are conveyed by a pipe 35 to a condenser 36 cooled with the usual water cooling means, from which the condensate passes into a vented sight glass 37 and from which part of the condensate passes by a pipe 38 back to the lid and benzol, passes out by the valved column through the pipe 34 while the remainder of the condensate is conveyed by a pipe 39 to'a tailbox 40 having a discharge pipe 41 leading to a stora e tank 42 provided with a valved draw-01% pipe 43.

When the reaction is complete in the still 1 the ethyl lactate containing traces of alcodraw-off pipe 3 to a still 44 heated by means of-a steam coil 45 and having a valved drawoff pipe 46 for conveying away the purified ethyl lactate. The vapors of alcohol and benzolpass out by'pipe 47 to a'condenser 48, cooled in the usual way with a current of water, from which the condensate is collected in one or more storage tanks 49 and 50 having a valved inlet pipe 51 and 52 leadng thereto. Connected to the pipe 52 there is also provided a vacuum pump 53 for securing the best available vacuum.

In carrying out my process the lactic acid and the alcohol in the still 1 are heated to a temperature of approximately 80 (3., thereby forming ethyl lactate while the water,

benzol and alco 01 pass into the column 6, from which vapors of water, benzol and alcohol are conveyed away for condensation, while alcohol and benzol are returned to the still 1 from the bottom of the column 6. The top of the column is continually sealed by a portion of the condensate from the dephlegmator 9 and the condenser 13, thus establishing, as far as possible, uniform conditions at the top of the column, as the top ofthe column is fed with a liquid very close in composition to the composition of the evolved vapors. This also enables the process to be conducted with a comparatively small quantity of benzol so that the condensate reaching the separating chamber 22 will be rich in the water to be removed. The remainder of the condensate is allowed to separate in the sep arating chamber 22 while the layer comprising principally benzol passes back into the column 6 without having been admixed'with an additional quantity of waterwhich will tend to make the benzol less dry and there-- part by weight of water to one part by weight of incoming liquid, thus removing the remaining benzol which accumulates at the top of the scrubber and is conveyed back by the pipe 27 to the column 6. The remaining water layer comprising dilute alcohol is subjected to rectification in the column 29, the lower portion of which is maintained at approximately 100 C., from the lower end of which water flows away, while the evolved vapors of 95% alcohol are condensed and collected in the storage tank 42. In order to secure an ester free from traces of alcohol and benzol the ethyl lactate is subjected to vacuum distillation in the still 44, ,maintained at a boiling temperature so as to recover the separated ethyl lactate and I mixed alcoholand benzol which latter may be used over again in the proces's.

It will be understood that other esters may be madein accordance with my process as, for example, ethyl oxalate, ethyl tartrate, ethylcitrate, ethyl chloracetate, ethyl esters of maleic acid. ethyl esters of malic acid and ethyl esters of succinic' acid, by esterification of the corresponding acids with ethyl alcohol. Furthermore, propyl alcohol or higher alcohols or polyatomic alcohol such 'as glycol or glycerol may be used instead of ethyl alcohol to produce the corresponding esters of any of these acids.

\Vhile I have described my invention in detail above many changes may be made in con iection with the same within the scope oi .uy-invention.

I claim:

1. The process which comprises esterifying an alcohol and an acid in the absence of a catalyst and in the presence of a third liquid miscible with the alcohol .but sub ,stantially immiscible with water. while removing from the reaction mixture vapors of 7 water, the alcohol and the third liquid, rectifying said vapors and separating the condensate into .two liquid layers without the addition 3 water, containing respectively high and low percentages of the third liquid.

2. The process which comprises esterifying an alcohol and an acidin the absence of a catalyst and in the presence of a third liquid miscible with thealcohol but substantially immiscible with water, while removing from the. reaction mixture vapors of water, the alcohol 'and the third liquid, rectifying said vapors,separating the condensate into two liquidlayers without the addition of water, containing respectively high and'low percentages of the third liquid,

and subjecting. the liquid layer containing the low percentage of the third liquid to washing to remove said third liquid therefrom.

. 3.'The process which comprises esterifying an alcohol and an acid in the absence of a catalyst and in the presence of a .third liquid miscible with the alcohol but substantially immiscible with water, while nemoving from the reaction mixture vapors of water, the alcohol and the third liquid, rectifying said vapors and separating the condensate into two liquid layers, containing respectively high and low percentages of the third liquid and running back into the rectifier the third liquid which has been separated out.

4. The process which comprises'esterifying an alcohol and an acid in the absence of a catalyst and in the presence of a third liquid miscible with the alcohol but substantially immiscible with water, while removing from the reaction mixture vapors of water,

the alcohol and the third liquid, rectifying said vapors, separating the condensate into two liquid layers containing respectively high and low percentages of the third liquid, subjecting the liquid layer containing the low percentage of the third liquid to wash- I ing to remove said third liquid therefrom,

and running back into the rectifier the third liquid which has been separated out.

5. The process which comprises esterifying ethyl alcohol and lactic acidin the presence of benzol, while removing from the reaction mixture vapors of water, the alcohol andjthe benzol, rectifying said vapors and separating the condensate into two liquid layers Without the addition of water, containing respectively high and, low percentages ofthe benzol.

6. The process which comprises esterifying ethylalcohol and lactic acid in the presenceofbenaol, while removing from the reaction .-mixture vapors of water, the alcohol and the 'benzol, rectifying ,said .vapors, separating 55 the condensate into two liquid layers without the addition of water, containing re spectively high and low'percen'tages ofthe benzol, and subjecting the liquid layer con taining thelow percentage of the benzol to washing to remove said benzol therefrom.

V Thep'rocess which comprises esterifying ethyl alcohol and lactic acid in the presence of benzol, while removing from the reactionmixture vapors of water, the-alcohol and the benzol, rectifying said vapors and separating the condensate into two liquid layers, containing respectively high and low percentages of the benzol and runnlng back into the rectifier and benzol which has been separated out.

8. The process which comprises esterifying ethyl alcohol and lactic acid in the presence of benzol while removing from the reaction mixture vapors of Water, the alcohol and the 1 benzol, rectifying said vapors, separating the condensate into two liquid layers, containing respectively high and low percentages of the benzol, subjecting the liquid layer containing the low percentage of'the V benzol to washing to remove said benzol therefrom, and running back into the rectn fier the benzol which vhas-beenseparated out.

ing an alcohol and an acid in the absence of f a catalyst and in thepresence of a third liquid, miscible with the alcohol but substantially immiscible'with the water, while removing from the reaction mixture vapors of water, the alcohol and the third liquid, rectifying said vapors and returning tothe top of the rectifier some of the condensate before separation of the same. 11; The process which comprises esterifying ethyl alcohol and lactic acid in the presence of benzol while removing from the reaction mixture vapors of water, the alcohol and the benzol, rectifying said vapors and returning to the top of the rectifier some of the condensate.

12. The process which comprises esterifying ethyl alcohol and lactic acid in the presence of benzol while removing from the reaction mixture vapors of water, the alcohol and the benzol, rectifying said vapors and returning to the top of the rectifier some of the condensate before separation. of the same.

13. The process which comprises esterifying.=an alcohol and an acid in the presence of a third liquid miscible with the alcohol I but substantially immiscible with water, while removing from the reaction mixture vapors of water, the alcohol and the third liquid, rectifying said vapors and separating the condensate into two liquidlayers, con-I taining respectively high and low percentages pf the third liquid and rectifying the remaining liquid containing water and the alcohol.

14. The processwhich comprises e'sterifying an alcohol and an acid in the absence of ing an alcohol and an acid in-the presence ofa catalyst. and inthe presence of a third. liquid miscible with the alcohol but sub-.

stantially immiscible with water, while removing from the reaction mixture vapors of water, the alcohol and the third-liquid, rectifying said vapors, separating the condensate into two liquid layers, containing respectively high and low percentages of the third liquid, subjecting the liquid layer containing the low percentages of the third liquid to washing to remove said liquid therefrom, and rectifying the remaining liquid containing water and the alcohol.

15. The process whichcomprises esterifying ethyl alcohol and lactic acid in the presence of benzol, while removing from the reaction mixture vapors of water, the alcohol and the benzol, rectifying said vapors and separating the condensate into two liquid layers, containing respectivel high and low percentages of the benzol an rectifying the remaining liquid containing water and'the alcohol.

16. The process which comprises esterifying ethyl alcohol and lactic acid in the presence of benzol, while removing from the reaction mixture vapors of water, the alcohol and the benzol, rectifying said vapors, separating the condensate into two liquid layers, containing respectively ,hi h and low percentages of the benzol, sub ecting the liquid layer containing the low percentage of the benzol to washing :to remove said benzol therefrom, and. rectifying the remaining liquid containing water and the alcohol.

17. The process which comprises esterifying an alcohol and an acid in the presence .of a third liquid miscible with the alcohol but substantially immiscible with water while removing from the reaction mixture vapors of water, the alcohol and the third liquid, and then distilling the resulting ester to re-- move the remaining alcohol and third liquid present therein.

18. The process which comprises esterifya thirdjliquid miscible with the alcohol but substantially immiscible with water, while removing from the reaction mixture vapors ing from the reaction mixture vapors of of water, the alcohol and the third liquid, and then distilling the resultin ester to remove the remaini alcohol an third liquid present therein wit the aid of a vacuum.

19. The process which comprises esterifying an alcohol-and an acid without the ald of a catalyst in the presence of a third liquid miscible with the alcohol but substantially immiscible with water, while removwater, the alcohol and the third 1iquid.

20. The process which comprises esterify-' ing ethyl alcohol and lactic acid without the aid of a catalyst in the presence of benzol, while removing from the reaction mixture vapors of water, the ethyl alcohol and the benzol.

21. The rocess which comprises esterifying ethyl a cohol and lactic acid in the presence of a third liquid miscible with the alcohol but substantially immiscible with water, whileremoving from the reaction mixture vapors of water, thealcohol and the third liquid, rectifying said vapors and separating the condensate into two liquid layers, containing respectively high and low percent ages of the third liquid.

22. The process which comprises esterifying an alcohol and an acid in the absence of a catalyst and in the presence of a third liquid miscible with the alcohol but substantially immiscible with water, while removing from the reaction mixture vapors of Water, the alcohol and the third liquid, rectifying said vapors and separating the condensate into two liquid layers, containing respectively high and low percentages of the third from the reaction mixture vapors of water,

the alcohol and the third liquid, rectifying said vapors and separating the condensate into two liquid layers, containing respectively high and low percentages of the third liquid, separating out the third liquid from the layer containing a small percentage thereof and rectifying the remaining liquid containing water and the alcohol.

24. Theprocess which comprises esterifying ethyl alcohol and lactic acid in the presence of a third liquid miscible with the alcohol but substantially immiscible with water while removing from the reaction mixture vapors of water, the alcohol and the third liquid, and then distilling the resulting-ester to remove the remaining alcohol and third liquid present therein.

25; The process which comprises esterifying ethyl alcohol and lactic acid in the presence of a third liquid miscible with the alcohol but substantially immiscible with water,

to remove the remaining alcohol and third.

while removing from the reactionmixture liquid present therein with the aid of a vacuum. In testimony that I claim the foregoin I have hereunto set my hand this 19th day of March, 1921.. i

JoHu A. STEFFENS. 

